Screen for driers



July 13, 1937. D. DALlN 2,086,699

sREEN Foa DRERs Filed- Ded. 1o, 1954 INHHHHIUNIllllllillll IlIlllIIllllllllllllllIlIlllIlI\IlIlllIlI\IlllIlllllllIllIllllllllllllllll\lIIHIHIIHMHHHHHEB y O o O Patented July 13, 1937 UNITED l STATES i-ui'irlvrv OFFICE y sonnen Fon Drums David Dalin, Milwaukee, Wis.

Application December This invention relates to driers and refers more particularly to `vacuum driers of the .type forming the subject matter of Letters Patent No. 2,034,860, issued to David Dalin, March' 24, 1936, with particular reference to the construction of the screens which cover the openings communicating the material receiving compartment with the x vapor chamber or suction compartment.

Heretofore, thekeeping of thesescreens clean presented a very'l perplexing problem and as the efficiency ofthe drier depends toa great extent upon'maintaining unrestricted flow of the gases and vapors from the drying materials, this problem was of primary importance. Thedifculty of keeping the screens clean in the earlier vacuum 4type'driers led to the adoption of expensive and complicated so-called self cleaning screens.

Generally, these so-called se1f cleaning screens incorporated blades arranged for movement across the screen plates or between sets of screen plates for the intended purpose of cutplates clean during the voperation of the apparatus. These devices obviously were complicated and expensive, and in practice did not function satisfactorily. The screen which the so-called self cleaning screen superseded, consisted of a perforated plate welded or otherwise secured to theoutside face of the wall having the openings through which the communication was established betweenthe material containing compartment and the vapor chamber.r These perforated plates were purposely `placed on the outside face of thewall dividing the two compartments on thetheory `that by keeping the screen out of contact with the material being dried, clogging would be avoided. In somevcases, the were even provided with outward extensions to locate the screens as far from the plane of the inside face of the w `ll as was compatible with accepted design.

Practice, however, demonstrated the fallacy of `this theory for regardless of how far the`.screens were moved outwardly of the inner face of the 45 screens and the perforations were soon not only by having the individual grains lodge in the perforations, but by the fine powdered mealy substance which inevitably forms in the drier 50 during operation.

'Y Consequently, this earliertype of screen,

openings through the end walls i to be at all useful, required cpnstant cleaning which.

entailedthe shutting down of the entire apparatus. i 55 n As hereinbefore noted, the failure of this earlier i will yappear through a 4screen 1o, 193i, kserial 10.156.199 4 claims.' (01534-5) type oi screen led to he a option of the complicated and expensive so-called self cleaning screens, -which ashas been seen, did not in anywise minimize the problem.

With these objections to past screen construc- 5 tions *in mind, it is therefore an object of. this invention to provide an improved screen particularly adaptable to vacuum driersoi the type described, which is so constructed that manual attention is .entirely obviated.

More specifically it is an object of this invention to provide a screen which is automatically kept clean by the action of the material being dried.

In the past where a perforated plate was eml5 ployed for thescreen, the plate was generally of substantial thickness. This was another source powdered material would accumulate in the outerends of the perforations from which it couldgnot be removed 2O except by manually cleaning the same, which entailed gettinginto thesuction chamber.

`It istherefore a further object of this invention to provide a screen ywhich issufiiciently thin so that accumulations. of Vpowdered vmaterial in the perforations thereof are removed by thermaterial itself projecting through the' perforations. With the above and other objects in view which A as the description proceeds, this invention resides in the novel construction, cornbination and arrangement vof parts substantially as hereinafterV4 described and more particularly defined bythe appended claims, it being understood that such changes in, theuprecise embodi- ,ment oi the hereindisclosed invention may be made as come within'the scope of the claims.

` The accompanying drawing illustrates several complete examples of the physical embodiment of the invention constructed according to the best modes so far devised for plication of .the principles thereof, and in which: Figure 1 is a view inv side elevation with parts broken away` and in section of. a vacuum type of drier embodying this-invention;

, Figure 2 is Figure 3 is a plan view of said screeened opening; v 4 f i v Figures 4 and 5 are cross section views through modified embodiments of this invention; Figure 6 is an enlarged cross section` view y construction illustrating the objectionable'features of past designs; and

Figures 'l and 8 are magnified cross section views through a portion of the screen to illus- 5:

the practical. ap- 40 an enlarged cross section'view 45 vthrough one of the screened openings;

vfthe nature of the trate the comparison between a thick screen plate and a thin screen plate.

Referring now more particularly to the accompanying drawing in which like numerals indicate like parts throughout the several views, the numeral 4 designates generally the drum of a vacuum type drier rotatably mounted in any suitable manner and caused to oscillate by means of a pinion 5 meshing with a ring gear 6, the pinion being driven alternately rst in one direction and then in the other by suitable driving means (not shown).

The drier drum has a material receiving compartment 'I closed at one end by a hollow bulkhead 8. The compartment] is adapted to be charged and discharged through an opening 9 provided with a removable cover I0. As brought out more in detail in the aforesaid copending application, a heat exchanger indicated generally by the numeral and comprising a plurality of hollow tubes communicating withthe interior of the hollow bulkhead` 8, extends through the compartment I to heat the material. The heat exchanger is supplied with a suitable heating medium through an inlet pipe I2, and the spent heating medium is exhausted from the the heat exchanger through an exhaust pipe I3. The hollow bulkhead 8, as stated closes one end of the material receiving compartment 1, and cooperates with the adjacent end wall I4 to dene a vapor chamber or suction compartment I5 which may be provided with a normally closed opening I6 through which access may be had to the interior thereof.

The end wall I4 has an axial opening I1 over which a nipple or discharge nozzle I8 is secured. A rubber duct I9 connected with an evacuator of any suitable design (not shown) is attached to the nipple I8 to provide for the evacuation of the vapor chamber without disturbing the oscillation of the drum.

'I'he hollow bulkhead ings 20 closed only by 8 has a plurality of, openscreens 2| so that theinterior of the material receiving compartment 'I is communicated with the vapor chamber to be evacuated to drawoi the vapors and moisture from the material being dried. and thus promote the drying process.

Obviously, if the eiliciency of the drier is to be maintained, the screens 2| must be kept clean to allow unrestricted passage of the vapors from the material receiving compartment into the vapor chamber I5. It is to this purpose that theA present invention is directed.

As pointed out' hereinbefore, the earlier type of screen consisted-of a perforated plate mounted on the outside surface of the partition wall, which in this instance is provided by thelphollow bulkhead 8. In the present instance, the screen also consists of a perforated plate but in thiscase, it

is mounted on the inside face of the hollow bulkhead, as shown.

Preferably the inside surface of the screen plate 2| is flush with the inside surface of the hollow bulkhead `8 so that there is no restriction to the free movement of the materialV across the inside surface of the screen plate. l

Itis also to be observed that the plate 2| is thin. It is comparatively thinner than the plates forming the walls of the hollow bulkhead or the other parts of the drum. 'Ihe thickness of the plate and the size of its apertures 22 is determined from material which the drier is fjdesigned to handle.

The purpose of restricting the thickness of the plate is illustrated by the comparative disclosures in Figures '7 land 8. As shown in Figure 7, if the plate is comparatively thick the individual kernels which will project into the openings 22 during the operation of the drier will not extend sufficiently far to dislodge the accumulation of fine powdered or mealy material 23 which is an inevitable development of the drier in operation; whereas, if vthe plate is comparatively thin, as shown in Figure 8, such accumulation of powdered or mealy material is constantly removed by the projection of the kernels through the openings 22. It is, of course, to be appreciated that the openings 22 are of such size as to prevent the complete passage of the individual kernels therethrough.

As hereinbefore pointed out, the screen plate is preferably flush with the inner surface of the bulkhead so that the material being dried is permitted to sweep unrestrictedly across the-surface of the screen plate. Consequently, the individual kernels which project intothe perforations of the screen are dislodged by the inherent action of the material itself. This action, as distinguished from the condition which exists where the screen plate is mounted on the outside surface of the bulkhead, may be appreciated from reference to Figure 6.

As shown in Figure 6, where the screen is removed outwardly from the plane ofthe inner area of the screen is materially reduced.

From the foregoing description taken in connection with the accompanying drawing, it will be readily apparent to those skilled in the art to which this invention appertains, that the salient taining compartment.

In each instance, the plate'is comparatively thin and is mounted so as to permit an unrestricted flow of material across its inner surface.

What I claim as my invention is:

1. In a grain drier of the vacuum type, a movably mounted container having a compartment to receive material to be dried, means through which air may be exhausted from the container to establish a vacuum therein', means for moving said container to cause material contained therein to move across one wall of the material receiving compartment, said wall having an opening through which vapors may be drawn from the material being dried, and a screen plate covering said opening to prevent the passage of the material being dried through the opening, said screen plate comprising a thin perforated plate whose perforations are of a size to prevent the passage therethrough or individual pieces of the material 76 being dried, and whose thickness is such that individual pieces lodged in the perforations project beyond the outer face of the plate so as to dislodge possible accumulations ofmealy matter in the perforations, and said plate being mounted so that the material moving within the container is free to sweep unrestrictedly across the inner surface of the plate so as to dislodge individual pieces of the material from the periorations.

2. vIn a vacuum type grain drier, a container to hold a quantity of material to be dried, means throughwhichy air may be exhausted from the container to establish a vacuum therein, means for moving` the container material across one wall of the container, said wall having an opening to allow for the passage of gases therethrough, and'a screen covering said opening to prevent the escape of the material l being dried through said opening, said screen comprising a thin perforated metal plate mounted so that the material moving across said wall has an unrestricted sweep across the inner sur,-

V face of the perforatedplate to dislodge particles of the material beingrdried from the perforations in the plate and the thickness of the plate being i such that individual particles of the material may project entirely through the perforations to dislodge` accumulations of mealymatter from the perforations.

3. In a device for treating granular material under vacuum, a movably mounted container for the material, means through which air may be exhausted from the container to establish a vacfor moving the container to back and uum therein, means v vcause the contents thereof to move accenno to cause motion of the' material may escape screen across said opening to prevent the passage comprising a perforated enable part of a kernel of grain to project throughr dislodge any accumulated mealy' forth across one of its walls, said wall having an opening through which gases may escape from the material, and. a screen over said opening comprising a perforated metal plate mounted substantially flush with the inner surface of said wall so as to allow the contents of the container to sweep unrestrictedly across plate being of such thickness with respect to the size of the individual kernels of the granular material that such individual kernels will project entirely through the apertures of the 'plate to dislodge any accumulations of mealy material in the perforations.

4. In a vacuum type grain conditioning apparatus, a container having a compartment for material to be treated, means through which air may befexhausted from the container to establish a vacuum therein, a partition wall defining one wall of the material receiving compartment and having an opening and .vaporsincidental to the treatment of the from the material, and a the opening, said screen plate sufficiently thin to of material' through its openings to matter and mounted so that the material within the container is free to sweep unrestrictedly across its entire inner surface, said opening and consequently thescreen being considerably smaller than the full area of the partition wall so that `the material may sweep across the screen with considerable velocity.

,DAVIDIDALIN.- y

the screen plate, and said therein through which gases 

